This invention relates to refrigeration systems with hot gas defrost.
Hot gas defrost is very effective and is especially useful with refrigeration systems in merchandising cabinets (also known as cases) in supermarkets where many food products have to be displayed in refrigerated cases. Many modem supermarkets are much larger than in the past, with the result that known hot gas defrost systems are somewhat expensive to install and operate and also contribute to product deterioration.
It is therefore an object of the present invention to provide a hot gas defrost system which is less expensive to install and operate than known systems and which enhance product storage.
According to the invention, a hot gas defrost system is provided with a dedicated defroster compressor, that is to say a compressor which functions in the defrost circuit only and is additional to the compressor or compressors which are provided in the main refrigeration system. The invention enables defrosting to be effected without affecting the normal operating pressures of the main compressor or comressors.
The present invention accordingly provides a method of defrosting a refrigeration system having a main compressor connected by a main hot gas discharge line to a condenser, said condenser being connected by a main liquid line to thermal expansion valves and subsequent cooling coils, each thermal expansion valve and cooling coil being in parallel connection with the other thermal expansion valves and cooling coils, each cooling coil being connected by a suction line to main compressor, said defrosting method including passing hot gas from the main hot gas discharge line through a selected cooling coil to defrost same, compressing cooled hot gas which has passed through the cooling coil by means of a separate dedicated defrost compressor, and returning the compressed hot gas to the main hot gas discharge line.
The hot defrost gas may also be passed through the main liquid line to flush out liquid refrigerant therefrom. Also, the cooled defrost gas may be heated by heat exchange with hot gas from the main hot gas discharge line.
The present invention also provides a refrigeration system with a hot gas defrost circuit, said refrigeration system including a main compressor connected by a main hot gas discharge line to a condenser, said condenser being connected by a main liquid line to thermal expansion valves and subsequent cooling coils, each thermal expansion valve and cooling coil being in parallel connection with the other thermal expansion valves and cooling coils, each cooling coil being connected by a suction line to said main compressor, each cooling coil being connected by a suction line to said compressor, and said hot gas defrosting circuit including a defrost hot gas supply line for supplying defrost hot gas from the main hot gas discharge line to a selected cooling coil, a defrost suction line to receive cooled hot gas from the cooling coil, a dedicated defroster compressor connected to the defrost suction line for compressing said cooled hot gas, and a defrost compressor output line for passing compressed hot defrost gas to said main hot gas discharge line.
The defrost hot gas supply line may also supply defrost hot gas to the main liquid line to flush out liquid refrigerant therefrom. Also, the system may also include a vaporizer through which the defrost hot gas and the cooled defrost hot gas pass in heat exchange relationship.